can you use a switching regulator from 120v AC (house power) 5 amp to output 5v DC 5 amp?
Sure, check out an ATX power supply for a PC computer. They are powered by 120VAC or 240VAC. Pins 21-23 are 5Vdc at near 30A (in parallel).
So I guess the only thing left is to current regulate the LEDs.  But at least now you are in the safe voltage range if you need to roll your own.


  Pinout Reference for ATX 24 pin 12V Power Connectors 
  
  Pin    Name    Wire Color Description 
  
  1 +3.3V   Orange  +3.3 VDC 
  
  2 +3.3V   Orange  +3.3 VDC
  
  3 COM Black   Ground 
  
  4 +5V Red +5 VDC 
  
  5 COM Black   Ground 
  
  6 +5V Red +5 VDC 
  
  7 COM Black   Ground 
  
  8 PWR_ON  Gray    Power Good 
  
  9 +5VSB   Purple  +5 VDC Standby 
  
  10    +12V1   Yellow  +12 VDC 
  
  11    +12V1   Yellow  +12 VDC
  
  12    +3.3V   Orange  +3.3 VDC 
  
  13    +3.3V   Orange  +3.3 VDC 
  
  14    -12V    Blue    -12 VDC
  
  15    COM Black   Ground 
  
  16    PS_ON#  Green   Power Supply On
  
  17    COM Black   Ground 
  
  18    COM Black   Ground 
  
  19    COM Black   Ground
  
  20    NC  White   -5 VDC (Optional - Removed in ATX12V v2.01) 
  
  21    +5V Red +5 VDC 
  
  22    +5V Red +5 VDC 
  
  23    +5V Red +5 VDC 
  
  24    COM Black   Ground