The numbers for 2017 alone:
Roughly 5m homes were sold in 2017. Assuming the median price of $200K was the average home sold, total transaction value would have been $1T. In other words, foreign transactions amounted to $153b out of $1T, or 15%. That's a pretty big number. If the units sold mirrored the dollars involved, 1 out of every 6 homes was sold to a foreigner.
$200,000 won’t buy an imported plastic communist Chinese dog house in Palo Alto/Silly-Con Valley.
at least not since so many imported plastic communist Chinese dogs have been buying up the (real) houses there