It has been remarkably, really.

The number of elite European soccer clubs who have been in the U.S. this summer is … astonishing.

Real Madrid. Bayern Munich. Manchester United. Manchester City. Liverpool, Arsenal.

Atletico Madrid, Roma, Inter Milan, AC Milan, Monaco, Olympiakos.

Those names look like most of the final 16 team in the European Champions League, and every one of them has traipsed through the U.S. this summer.

Why did they make the trip over the Pond?

First, let’s flesh out the list a bit, with even more British teams.

Tottenham. Crystal Palace. Aston Villa. Fulham. West Bromwich Albion. Swansea City, a Welch club but a member of the English Premier League. All of them were here.

Three of the top four Premier League teams from last season have been in the U.S., and five of the top seven. And no fewer than 11 of the 20 sides who played in the Premier League last season cleared customs at U.S. airports. (Fulham was relegated, so 10 of the current 20 Premier League clubs.)

All of those European clubs played at least two friendlies in the U.S., and several played more. Manchester United, probabl;y the most popular international club in the U.S., could play no fewer than five matches in the States in a span of 13 days.

So, why did they cross the Atlantic?

The simple answer is one word:

Money.

First, big clubs like to get into game shape against other clubs. Preferably before a big crowd. No intersquad matches behind closed doors, for these guys.

Second, the U.S. is seen as one of the last largely untapped markets for international club soccer.

The belief among many of those Euro clubs, especially the monsters like Bayern, Real Madrid, Liverpool and the two Manchesters, is that they have done their due diligence spending summers flying in the opposite direction. To Asia.

Most of them, particularly the English big clubs and Spain’s Big Two (Real Madrid and Barcelona), feel as if they already have their hooks into Eurasia, and are selling about as many jerseys as they are likely to sell without some big and renewed effort. Sort of a “diminishing returns” scenario. (Plus, journeys to Asia can get a little weird, like the Asia Trophy in Hong Kong, last summer, where City, Tottenham, Sunderland and a local team played in a swamp, and a couple of players got hurt.

Meanwhile, trips to the U.S. mean high ticket prices and big “gates”, as well as the potential for making new fans who will buy the high-end types of jerseys and scarves that buff up the bottom line.

But at the same time, the U.S. is easy, once the plane ride is over. The facilities the teams train at and play in are big and nice. The hotels are posh but discrete. Security concerns are minimal.

Yet, the country also offers a bit of anonymity for the visiting footballers, which they often appreciate.

The lads at Manchester United can hardly venture outside their doors, back home, without someone getting in their faces. But in the U.S. … 90 percent of Americans, maybe 95 percent of Americans, don’t know Wayne Rooney from Mickey Rooney.

I am fairly convinced that the players of Real Madrid and Bayern, two of the strongest clubs in the world, as well as best-known, could amble through any mall in America and rarely be recognized.

OK, maybe not Cristiano Ronaldo. But everyone else.

The lesser English clubs came over and played friendlies, mostly with Major League Soccer teams.

Check the schedule on July 23. And then on July 26. Crazy numbers of games going on. Seems like every team in the MLS played some major club, at some point. (And generally lost, aside from New York Red Bull, which defeated Arsenal 1-0.)

The big event, however, and what ultimately may have been key in bringing over so many prominent sides, was the International Champions Cup, featuring eight teams in two groups of four, with the winners of the groups meeting in Miami on Monday for the championship.

That tournament reeled in Real Madrid, Manchester United, Roma and Inter, in Group A, and Manchester City, Liverpool, AC Milan and Olympiakos in Group B.

United has played before the biggest crowds — more than 84,000 at the Rose Bowl to see them nuke the Galaxy 7-0;  54,000 in Denver to see them play Roma; 61,000 at Landover, Maryland, to see them beat Inter.

Their game with Real Madrid on Saturday could set a record for a soccer crowd in the U.S., at the Big House at the University of Michigan, where more than 100,000 could turn up.

It isn’t all sweetness and light, for the visitors. They often feel as if they are being run ragged even before their interimable league schedules begin. Not to mention, national cup tournaments and the Champions League grind, for the big clubs. (Fulham doesn’t have to worry about much of this.)

Louis van Gaal, new coach of Manchester United, has made clear he wishes they were not spending so much time in the States (more than two weeks) and playing so often with another long trip across the Atlantic ahead of them, and he seems intent on making sure the club’s marketing department doesn’t continue to be the tail that wags the dog.

(Though the boys in marketing probably see the players as the tail.)

We can figure on more Euro clubs coming over in the future, until they feel as if they have maxed out their earning potential here.

But will as many come over as have this year?

Hard to imagine.