The $20 billion may cover initial claims, but will be insufficient (NY Times opinion).

If the flow is 60,000 bbl/day, over the 60 days,that is 3,600,000 bbl. (41 gallons/US oil barrel) so far. By mid-August (if all goes well!) a relief well will intersect the flow. That's another 60 days, so about 7.2 million barrels.

The Mexican gusher did not attract the attention of Americans to a great extent because effects on Texas areas of the Gulf were only moderate. The BP Macondo gusher affects millions of Americans directly.
Two relief wells took many months to stop the Mexican flow, and both water depth and sediment depth were less. The BP well also encountered a formation where the gas pressure is high, moreover the volume of gas relative to liquid petroleum is high.

Tony Hayward's testimony at the Congressional hearing had much of an "I don't know" and the "investigation is incomplete" flavor, although some 59 days have passed since the blowout- Nonsense!