It would seem the sequestration budget has mostly affected U S Customs and Border Protection. USCBP has cut back most overtime, meaning Immigration and Customs processing can take noticeably longer at your intended Port of Entry (or at preclearance station). At LAX, for example, lengthy delays have even followed international arrivals passengers being held on the aircraft as long as one hour prior to being allowed terminal entry (as reported a couple of weeks ago in USA Today).
We noticed a distinct delay passing through Immigration at NAS preclearing to the USA earlier this month - check-in queues were quite light, as were security queues - it took a long time, perhaps 3/4 hour, to process USCBP. We were told this was because we showed up before normal working hours and they had reduced personnel to avoid paying overtime.
At DFW arriving from MAD, no major problems I noticed - but we arrived at an hour with no other international arrivals, and we have Global Entry.
Mod hat on: This is not an AA-related issue. It should be discussed in the appropriate fora - destination in some cases, but in most cases, Travel Safety/Security > Practical Travel Safety Issues.