Actually, even in a downturn, kicking out H-1B's may well do more harm than good for US citizens on average.

1. The person who has to leave won't use any goods/services in America anymore, further decreasing demand on the economy at the worst time. H-1B's are generally well paid and can afford to spend money on goods/services when employed, which probably usually sums up to more than one job's worth of labor (and not just unskilled labor, things like legal counsel too). Especially if they have family. In particular, while they are still unemployed they cost 0 jobs but still consume, so kicking them out is a guaranteed net negative until they find the next job. Which they would be most likely to do when the upturn begins, at which point it wouldn't matter anymore.

2. They are laid off and didn't find a new job. So they _aren't_ consuming a job in the US that an American could have filled - instead, the job is gone. On the contrary - if they _had_ retained/found a job in the 60 day window, they would have been allowed to stay. And they might not have gotten a new job before the next economic upturn. So the expected cost of letting them stay is more than 0 jobs but also less than 1 job.

3. It might help improve the odds for current job seekers competing for a limited job pool, but as H-1B's are on average highly qualified (the H-1B category is for specialty occupations), the job that the H-1B might have held will still not be available to most Americans and companies will probably end up with worse qualified employees (otherwise they wouldn't have hired an H-1B in the first place). So companies will be worse off, which is probably also bad for Americans as a whole on average. And those Americans who are likely hit hardest by the downturn - lower skilled labor - don't benefit from it at all.

4. The reduced supply of highly qualified labor may contribute to delaying the next economic upturn. This can have very severe mid term consequences. We see this in other areas, for example the chip shortage is _still_ causing serious issues. And considering how slow the US immigration system moves, it unlikely a (skilled) labor shortage would be any easier to solve than a chip shortage.

5. Kicking H-1B's out also means they will take any property and savings with them, instead of keeping them in the US market. Tech worker investments can be significant.

6. It is possible that their departure may lead to a job moving overseas, which is strictly worse for Americans than the job being in America and just held by a non-American (taxes etc.). Both because of reduced high skilled labor supply in the US, and because if they were already attractive enough to be employed as an H-1B, imagine how attractive it would be to get the same employee overseas, at a lower price point, and maybe with a better chance of long term retention if the company works on a new H-1B with them. All the US labor market protection mechanisms (prevailing wage determination, labor market test, etc.) don't apply to non-US subsidiaries...

Also, not deported. Deportation is one option for what happens after breaking laws and being put in removal proceedings (another would be voluntary departure). All H-1B's that I know are acutely cognizant of immigration laws and would leave if they can't find a job rather than risk incurring a ban. Either in 60 days, or maybe longer after applying for a period of satisfactory departure. Of course this distinction is primarily important for that person; the outcome for those who stay may be the same but let's have empathy.