I don't think that the central issue on drugs is about importing.  This 
is certainly an important issue for the drug companies that have 
exclusive access to the Medicare D program introduced by GW Bush in 
2003.  Amazingly, this is one of the few federal programs that does not 
allow for competitive bidding.  This single issue inflates drug prices 
in the US and makes drug prices much lower in other countries that use 
the purchasing power of their programs to drive prices down.
The history goes back to the Truman administration and illustrates why 
health care legislation has been so difficult.  You might enjoy a very 
good history of this at: 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2690175/
Briefly, coverage of drug costs was not included when Medicare was 
finally introduced in 1965 because of concerns about the cost.  It was 
not until 2003 when Medicare D was introduced by the GW Bush that any 
coverage was provided.  Why then?  Basically this relates to the battle 
that raged between Democrats and Republicans over cost.  The Democrats 
fought to protect the "bill for service" approach used in Medicare A and 
B while the Republicans fought to introduce Medicare C which limited 
future cost liability with a fixed price per individual "managed care" 
approach.  Unfortunately, Medicare C was failing when GW Bush took 
office.  Something new was needed to salvage it and that something new 
was Medicare Advantage which included drug coverage.  The compromise 
that the GW Bush administration made to make the bailout of Medicare C 
seem less obvious was the introduction of Medicare D which opened drug 
coverage to other Medicare plans, albeit at a cost.  The most 
controversial issue at the time was the absence of using the Medicare 
market to force competitive bidding, a problem that continues to plague 
us.
This issue carried over into the debates that raged over the ACA 
(Obamacare).  In order to get anything passed, the Obama administration 
avoided tampering with the cash cow that the drug companies enjoyed.
The issue of building the ACA around a single payer system like Medicare 
was ultimately abandoned by the House in favor of a public option.  Let 
the individual customers of insurance decide if they wanted private 
insurance or government insurance.  In the heat of this debate in the 
Senate, drug coverage was at most a side issue that had already been 
conceded.  Ultimately variations of the public option were offered in an 
attempt to save it including opt-in and opt-out proposals.  It was Joe 
Lieberman who put the final nail in the coffin for the public option.  I 
also blame Harry Reid who refused to change the Senate rules to allow a 
majority vote, keeping intact the Republican strength in the filibuster. 
  I also fault Max Baucus who gave away his majority advantage in the 
Senate Finance Committee by creating his infamous "Gang of eight" which 
succeeded only in wasting a lot of time thereby allowing opposition to 
build in the very public campaign by the health care industry to kill 
the ACA over the summer of 2009.  He could have brought the House bill 
to the Senate floor in July and the public option would have been part 
of the ACA.
The message in all of this is the massive influence that the industry 
has on politicians including the Democrats that I mentioned above.