Is is ok to try to stop people from breaking the law to sell Americans things they want?
Yes - reference illegal drugs, fake / counterfeit / stolen goods / child pornography / etc... and spending billions of dollars is one of the ways we keep an orderly law abiding society where your freedoms, property and personal protection are provided.
The law and order argument or a society with the rule of law is the real reason for our prosperity and hence the reason why everyone wants to come here or other countries with strong rule of law / low corruption, which is basically the opposite of their nations. If you ignore the law and just shrug when it is broken very soon you will be just like the countries these people flee from. The free market is great but it only exists when it has a place where rules are enforced and standards are universally applied. Disregard it and we will inevitably decline to place where factions impose their will on others other than by the rule of law adopted and applied thru democratic means with boundaries to protect minority political views and ensure basic rights.
You assume that one these people will contribute more in taxes than they will receive in services, that is highly unlikely as they are likely to be in low wage occupations, have a higher chance due to the nature of their occupations to become disabled, use more services than the native population as they immigrate and establish themselves in the US and yes, if leaders, cultural and political, from countries where people come from say hostile things not only "mean" to the US but to Western Civilization we should think twice about allowing large numbers of them in. It is naïve to an extreme to believe there is not some residual affinity for the mother country and it's culture / politics. Not racist but realistic, societies particularly free & tolerant ones are fragile things in reality and can be damaged easily, we need to be very prudent and cautious with ours.
As to excluding people from around the world from the American Dream, not everyone can come here. We have finite opportunities and finite ability to absorb and it is not me by myself to decide that but us as a nation thru our democratic process. More jobs not less are going to become automated, we have enormous amounts of our own population we callously gave up on and a tight labor market is better for more people in a nation rather than a saturation of workers putting a disproportionate amount of power in the hands of employers.