The calamity of suffering and destruction by Hurricane Irma in Puerto Rico is on a much greater scale than what Houston and Florida suffered for a variety or reasons. First, as gleaned from media accounts, Irma struck with much greater intensity, apparently destroying all but the most durable structures, including nearly all infrastructure facilities, bringing the island country to total paralysis. Parts of Houston suffered greatly, but were adjacent to unaffected areas that could offer immediate refuge and assistance. The main damage there, if I am not mistaken, was from flooding, which at extensive cost could be expected to return to normalcy within a reasonable time period.
No such prediction for return to normalcy seems feasible for Puerto Rico. The situation there is complicated by its isolation from the U.S. mainland. Furthermore, the extent of damage appears far beyond what FIMA and other emergency resources are prepared to deal with, especially with the concurrent disasters.
But there are other historical factors plaguing Puerto Rico's recovery, which you can look up in Wikipedia. Puerto Rico (= Rich Port) was a comparatively wealthy Spanish colony, benefitting mainly from sugar exports. The USA took ownership after the Spanish-American War, and it gradually shifted its economy to tourism and manufacturing of pharmaceuticals, textiles, electronics, and chemicals by U.S. companies attracted by special tax incentives. These favorable tax policies expired in 2013, which along with other factors, contributed to Puerto Rico's virtual bankruptcy prior to Hurricane Irma. Although its industries provided jobs, the profits from its U.S. dominated industries did not stay on the island, as is typical of colonies.
Perhaps the most significant obstacle to Puerto Rico's recovery is its status relative to the USA. Although its citizens are U.S. citizens, Puerto Rico remains a territory ultimately controlled by the U.S. Congress, which can determine its political and economic fate. (The United Nations Committee on Decolonization calls for the U.S. to expedite self-determination for Puerto Rico.)
Puerto Rico, then, is like a foster child of the USA, and therefore Congress should assume full responsibility for its welfare. That could mean providing all essentials for the population and evacuating them, if necessary, to the continental USA while reconstruction is in progress.
As an added thought, Puerto Rico presents an unusual opportunity to be a laboratory for the future. To rebuild as it was would expose it to the predicted ravages of future super hurricanes. No - it should be rebuilt to new standards that could much better withstand the onslaught of 150 MPH winds. Houses could be built with low profiles and steel skeletons well-anchored to the earth. Power grids could be placed underground and localized, using solar power, etc.
The cost would be huge, of course. Token grants and subsidies would not cover it. Congress should pass a special tax for Puerto Rico's recovery, or levy a permanent tax for environmental disasters. (Perhaps all we can expect from the current Congress is to rename it Puerto Pobre.) This is no time for general tax reforms to lower taxes.