Well, generally this is made under the assumption of operating in the real world and knowing that welfare won't be abolished.
The only reason why people go on welfare is because they need money. If they can get this money through getting a better job, then no welfare is necessary. People aren't that lazy and they want to work. They just don't know how.
Also, it could be argued that it hurts national unity if you don't learn the native language.
In the long term, this isn't the case. In the 1920s, immigrants interbred with each other, and with native born Americans, and their offspring was American by default. In the short term, there was some cultural division. But this went away as the immigrants assiliminated to their country on their own, interbred with Americans and other immigrants, and the kids ended up being completely assiliminated.
If you can't understand people because they are speaking Portuguese, Spanish, German, Russia, etc, how can you get along with them?
Google translate and their offspring, which tend to be bilingual. Just as people in the 1920s managed to assimilate to the US as time went on, the same thing would happen with this new batch of immigrants.
Second, presumably Americans have been paying into welfare for 10-20 years, whereas immigrants have not.
I don't think every American pays into welfare. Some get it without paying. The people on welfare I don't think get off of it ever generally, but I might be wrong on this.
Generally, retirement is when you have saved up a lot of money and no longer need to work.
Retirement for some people is like that, but retirement is also when someone hits the retirement age and gets social security benefits.
but considering we can't just get rid of welfare
I think it's possible to do this. Low income people merely need to be shown where the better jobs are and they would go to those better jobs, thereby eliminating their need for welfare.
The combination of wage destruction
History confirms that wages won't get destroyed. A common fear of hiring women during WWII was that they would cut wages by 50%. This did not happen, and because of the huge influx of female workers, the US economy skyrocketed. I think a similar thing would happen with these immigrants.