The irony is so thick here!
I guess Google, Amazon et al don't want competition in collecting data on US citizens from the government...
I'm not sure why they are even wading in on this. While I agree 100% that the government has no business building/using such a database, these tech companies have no dog in this fight. They are up to their necks in shit, so calling out the government for being waist deep in shit isn't helping.
Apple (who interestingly was not among the list of companies signing it) has the right idea - just try to lock everything down so the government can't find anything to add to their database from their customer's use of Apple products. The government is going to do what its going to do, irrespective of what Silicon Valley wants. In the current political climate, having all these tech companies weigh in probably makes it less likely for otherwise libertarian-leaning republicans to support their view, since they contribute significantly more to democrats than they do republicans.