The problem with your line of thinking is three fold.
1) remittances. While the US does import a lot of people, the economic benefit to the nation is greatly reduced by remittances.
2) Immigration is an ebb and flow type thing, during good times people run to the US but during bad times? There have been several years where the H1B quota was far from reached.
3) Depending on immigration for your long term future is risky. Other nations compete for them, and as the situation at home improves this reduces the advantage.
My country (Canada) is hooked on "immigration is our future" as well.. But there is negative news about this approach recently.
India newspapers have been running stories about how Canada only wants "low cost labour"...
If this continues, will Canada be able to attract people?
It's not the same at all.