People were buying overvalued homes they couldn't afford in the middle of nowhere on subprime adjustable mortgages, which caused the crash of '07 when the ARM rates kicked in and they couldn't afford payments. This is a fundamentally different situation.
Now, a very small number of elite highly wealthy people from around the world are treating American housing stock as their investment vehicles since there is literally no other better option in 2018. Where we go from here in terms of affordable housing, nobody knows. But I really really doubt we're going to see a housing crash any time soon. It's just simple supply and demand.
That was the complaint in Vancouver until they actually started tracking foreigner purchases and it turned out it was 10-15% of purchases (higher in certain neighborhoods). That means the other 85-90% of demand was from Canadians.
I recall this specifically, as I was in the market for a house at the time. Fortunately, I didn't face much cash competition as I was shopping slightly upmarket. The line seemed to be $300-400k. Those folks would be seeing pretty good returns at this point as those houses are now typically worth $500-600k and might be renting for $2-3k.
Not saying a crash is imminent, but prices are even higher than before last crash, even taking inflation into account.