I have just come back from a 10-day trip to Arizona to build hours. It is significantly less expensive than flying in the UK and (in Arizona at least) and flyable days/hours are more predictable.
I was based in Phoenix and the cost of flying there (Piper Cherokee 140) was about £83 per hour. (There would be cheaper options in the US but I was prepared to pay some extra for reliability.) When I added in the cost of airfares, hotel, car rental, travel insurance including flying cover, charts, dual check-out etc it came out at £119 per solo hour. This is much less than the cost of flying from my flying club in the UK (Piper Warrior £140 - £165 per hour plus landing fees at the landaway and transport costs to/from the airport).
Equally importantly, I could take a specified time away from work and be fairly confident I would get the hours I planned. I don't get paid for days I don't work so taking a week off to fly in the UK and spending some of it grounded because the weather is unflyable is expensive. For those who have more flexibility in their work hours, or who aren't working, the UK might be a more cost-competitive option.
In Arizona, I did 42 solo hours in 8 days. It is of course up to you whether you use your hours for productive learning or just fly back and forth from the same airport many times. I did high altitude and mountain flying, transits over Phoenix Internal Airport (very cool!) and through Class D airspace, flew into the Palm Springs Terminal Radar Services Area (TRSA) which has its own specific rules, and landed at 15 different airports to make the most of those "no landing fees"
There are some interesting places to visit too: flying over the Grand Canyon, through Monument Valley, and looking at volcanic and meteorite craters are memorable.
The types of flying I didn't experience were cross-wind landings and managing adverse weather, but I get plenty of practice with those in the UK
Getting hours in the US can be cost-effective and can be a good learning experience if you look at the total costs, time available, and type of learning you need.