Are ICAO and FAA airport signs and markings the same or are there differences? If so what are the differences?
ICAO Airport markings are defined by ICAO in Annex 14 of Chicago Convention, Aerodromes.
ICAO also requires at section 5.8 Notification of differences in the AIP of Doc 8126 Aeronautical Information Services Manual, that differences are explained in the country AIP, Section GEN 1.7 Differences from ICAO Standards, Recommended Practices and Procedures.
US regulations are not entirely compliant with ICAO SARP, and differences exist for airport marking.
Example of ICAO SARP
For the touchdown zone lights, ICAO states in Annex 14, at paragraph 126.96.36.199:
The lateral spacing between the innermost lights of a pair of barrettes shall be equal to the lateral spacing selected for the touchdown zone marking. The longitudinal spacing between pairs of barrettes shall be either 30 m or 60 m.
As US regulations are not fully compliant, the differences are explained in GEN 1.7 of the US AIP, page 129:
U.S. does not require the lateral spacing of touchdown zone lights to be equal to that of touchdown zone marking when runways are less that 45 meters wide.
All differences can be found at this location, sorted by ICAO reference and chapter. Differences related to Annex 14 start on page 124 (actually labeled GEN 1.7 81). Listing all of them (15 pages in the AIP) would be too broad for this answer.